(i) Field of the Invention
The present invention relates to a photo-setting resin composition useful to prepare a color filter, and a method for preparing the color filter by the use of the composition.
(ii) Description of the Related Art
As methods for preparing color filters, there have been heretofore known a gelatin dyeing method, a pigment disperse method, an electrodeposition method, a printing method and the like [Flat Panel Display '90, pp. 272; Flat Panel Display '91, pp. 129; and Kinki Chemical Association Functional Dyestuff Section Society-Electronics Section Society Public Lecture Data (Nov. 20, 1991)].
The gelatin dyeing method is a method which comprises coating a substrate with a gelatin coating film provided with photosensitive properties of a dyed medium, carrying out irradiation of ultraviolet rays and aqueous development to form a relief pattern, and then dyeing this relief pattern with a dye. The pigment disperse method is a method which comprises coating a substrate with a photo-sensitive colored resist in which a pigment is uniformly dispersed, as in the case of the dyeing method, followed by exposure and development to form a predetermined pattern. Moreover, the electrodeposition method is a method which comprises electrochemically depositing, on an electrode, a polymeric resin solution in which a pigment is dispersed. Furthermore, the printing method is a method which comprises directly carrying out printing on a substrate by the use of an ink in which a pigment is dispersed.
In addition, as a quality improvement method for the color filter, a polyimide-dye mixing method is disclosed in Japanese Patent Application Laid-open No. 77804/1986.
Among the above-mentioned preparation methods, the pigment disperse method has been employed as a mass production technique from the viewpoint of durability and workability, and the preparation of the color filters is tried by this technique. Furthermore, the gelatin dyeing method has been employed from the viewpoint of light transmission properties.
However, with regard to the pigment disperse method, a pigment is insoluble in a photo-cured resin which is a binder. Therefore, when the filter obtained thereby is used for a liquid crystal display, light is scattered by pigment particles, so that polarization deteriorates to give rise to a depolarization effect that contrast on the liquid crystal display declines. With regard to the gelatin-dye dyeing method, the durability of the obtained filter is poor. In addition, when two or more colors are applied to one substrate, a color protection film of an acrylic resin, a urethane resin, an epoxy resin or the like must be formed after one color has been given, or alternatively the surface of a dyed medium must be chemically treated with tannic acid or the like to prevent color mixing, which makes the preparation process complex.
With regard to the polyimide-dye mixing method, the light transmission of the polyimide resin is poor, and its preparation process is inconveniently complex. Since an organic solvent such as N-methylpyrrolidone is used, this method is not good in point of environmental pollution.